This event is free and open to the public. Register Here. Scientists often seem to be asking obscure theoretical questions. But sometimes asking such questions and doggedly following the answers leads to unexpected practical payoffs, as well as deep insights into how the world works. Physicist Philip Nelson will explore how the question “What is light?” leads to an understanding of how we see and to some powerful new ways to do so. If you have any questions about the event, please e-mail Julian Shendelman at juliansh@upenn.edu.